A new generation of insect larvae is eating the roots of genetically engineered corn intended to be resistant to such pests. The failure of Monsanto’s genetically modified Bt corn could be the most serious threat ever to a genetically modified crop in the U.S.

The strain of corn, engineered to kill the larvae of beetles, such as the corn rootworm, contains a gene copied from an insect-killing bacterium called Bacillus thuringiensis, or Bt.

But even though a scientific advisory panel warned the Environmental Protection Agency (EPA) that the threat of insects developing resistance was high, Monsanto argued that the steps necessary to prevent such an occurrence — which would have entailed less of the corn being planted — were an unnecessary precaution, and the EPA naively agreed.

“The scientists who called for caution now are saying ‘I told you so,’ because there are signs that a new strain of resistant rootworms is emerging…[A] committee of experts at the EPA is now recommending that biotech companies put into action, for the first time, a ‘remedial action plan’ aimed at stopping the spread of such resistant insects …

The EPA’s experts also are suggesting that the agency reconsider its approval of a new kind of rootworm-killing corn, which Monsanto calls SmartStax.This new version of Bt corn includes two different Bt genes that are supposed to kill the rootworm in different ways. This should help prevent resistance from emerging, and the EPA is allowing farmers to plant it on up to 95 percent of their corn acres. But if one of those genes is already compromised… such a high percentage of Bt corn could rapidly produce insects that are resistant to the second one, too.”